Rated 5 out of 5 stars

Installing the previous version (3.5) does seem to fix the problem. Though, when starting Thunderbird, there is now a slight delay (less than a second) before the standard button icons are replaced with the Phoenity ones. No big deal, it's acceptable. Thanks for the fix! Continue the good work... Maybe more custom sets of icons?

This review is for a previous version of the add-on (3.5).  This user has a previous review of this add-on.